Novel polybasic propellant

ABSTRACT

A NOVEL PROCESS FOR THE PREPARATION OF A POLYBASIC PROPELLANT POWDER HAVING A PROGRESSIVE RATE OF COMBUSTION BY FORMING A POLYBASIC PROPELLANT CONTAINING WATER-SOLUBLE, NITROGEN-RICH COMPOUNDS, TREATING THE SAID PROPELLANT WITH AN AQUEOUS MEDIA TO DISSOLVE THE SAID WATER-SOLUBLE COMPOUND OUT OF THE SURFACE LAYER AND INTRODUCING INTO THE RESULTING PORES A DESENSITIZER TO CONTROL THE RATE OF COMBUSTION AND THE PROPELLANT PRODUCED BY THE PROCESS.

United States Patent M 3,702,792 NOVEL POLYBASIC PROPELLANT HelmuthNolte and Paul Lindemann, Waldkraihurg, and

Walter Hahn, Aschau, Germany, assignors to Wasagchemie G.m.b.H. Munich,Lowengrube, Germany No Drawing. Filed Sept. 15, 1971, Ser. No. 180,853

Int. Cl. C06b 19/02 US. Cl. 149-10 9 Claims ABSTRACT OF THE DISCLOSURE Anovel process for the preparation of 'a polybasic propellant powderhaving a progressive rate of combustion by forming a polybasicpropellant containing water-soluble, nitrogen-rich compounds, treatingthe said propellant with an aqueous media to dissolve the saidwater-soluble compound out of the surface layer and introducing into theresulting pores a desensitizer to control the rate of combustion and thepropellant produced by the process.

STATE OF THE ART Heretofore, only nitrocellulose powders (so-calledmono'basic powders) have been used for weapons of high ballistic power.In order to coordinate the rate of combustion of these propellantpowders to the processes in the combustion area of the weaponsoptimally, the said powders were subjected to a surface treatment.Thereby, it was possible to delay the evolution of gas in the initialphase of the combustion which determines the maximum gas pressure. Aftercombustion of the desensitized zones, an intensified evolution of gasoccurs, leading to a progressive combustion which insures a favorableutilization of the propellant powder in the weapon.

The performance data for weapons of high ballistic power have beenincreasing continually, but nitrocellulose powders do not have thechemical and thermodynamic perequisites for a major increase inefiiciency. Therefore, attempts have been made to use polybasicpropellant powders for these weapons. The desired high muzzle energy andthe usually extremely restricted combustion areas require a considerableincrease of the energy potential. In order to maintain the gas pressureswithin acceptable limits, therefore, a greatly progressive combustion ofthe powder grain is required. A polybasic powder of nitroglycerine,nitrocellulose and nitroguanidine, for example, can be produced by knownprocedures also for weapons of high ballistic power, but the combustioncurve of this powder, determined in the 300 cc.-manometric bomb, ishighly degressive.

It is known from the literature that dibasic and polybasic powderscannot be surface-treated (Brunswig, Das rauchlose Pulver (Smokelesspowder), Berlin and Leipzig 1926, p. 274; Stettbacher, Die Schiess-undSprengstoffe (Firing and blasting materials), Liepzig 1933, p. 193).Although tribasic powders are made with the aid of small quantities ofvolatile solvents, they show under the microscope, similar to pureblasting oil powders, a sealed, homogeneous surface.

OBJECTS OF THE INVENTION It is an object of the invention to provide anovel polybasic propellant suitable for use in weapons of high ballisticpower.

It is another object of the invention to provide a novel process for thepreparation of polybasic propellant powders.

These and other objects and advantages of the invention will becomeobvious from the following detailed description.

The novel process of the invention for the preparation of a polybasicpropellant powder having a progressive rate of combustion, particularlyin the initial stages, suitable for high combustion power weaponscomprises forming a polybasic powder propellant containing awater-soluble, nitrogen-rich compound, surface treating the resultingpropellant with an aqueous media to dissolve the said water-solublecompound from the outer layers of the propellant and introducing intothe resulting pores in the propellant and on the surface of the charge adesensitizer to obtain a polybasic propellant with a progressivecombustion rate. The aqueous treatment may be effected at temperaturesfrom 15 to 100 C., preferably 50 to C.

The poly-basic powder propellant may be made of nitrocellulose andnitric acid esters of multivalent alcohols and will contain 20 to 60% byweight of a water-soluble, nitrogen-rich compound such asnitroguanidine, guanidine nitrate, ammonium nitrate, or dicyanodiamide.

This surface treatment of polybasic propellant permits the introductionof desensitizer-s, either in a single step or multistep treatment, to beadded into the cavities to a predetermined depth so that the aftercombustion of the outer layer and upon beginning of the projectilemovement, progressive combustion results so that the propellant may beused in high ballistic power weapons.

In a modification of the process of the invention, after the firsttreatment and/or following treatment stages, an intermediate wet storageof the solvent-moist powder is interposed or between the individualtreatment stages, there may be an intermediate dry storage of thepowder. In another modification, a Water treatment may be interposedbetween the individual treatment stages and/or before the final dryingof the powder.

The dissolving out of the water-soluble, nitrogen-rich compounds may beeffected by a pretreatment of the powder propellant for half an hourwith continuous agitation with water of a temperature of +50 C. in theratio of 1 part powder per 3 parts water proves expedient. Addition of adye allows the depth of penetration of the water into the powder grainto be observed by means of microtome section. The progress of thetreatment is determined quantitatively.

Pretreatment with water of +50 C.

Dissolved quantity of nitroguanidine in percent of the treatedpropellant:

This dissolving out brings about a lowering of the caloric content inthe pretreated layer, so that the total heat of explosion of the powderdrops after a half-hour extraction from 1130 cal/g. to 112 cal/g. andafter a two-hour extraction to 1108 cal/ g.

A powder propellant thus prepared is subjected to a surface treatmentwith desensitizers such as camphor, centralite (diphenylureaderivatives), urethanes and phthalates in alcohol solution, and it isexpedient to choose twoor multi-stage surface treatments with interposedintermediate wet storages or intermediate dry storages. The surfacetreatment is preferably carried out at about +40 C. with an intermediatedrying at 50 55 C. In special cases, a water treatment may be providedafter the last treatment stage and before drying, to remove solvents.The powder propellant thus treated is then finished in the usual manner.

In the following example there is described a preferred embodiment toillustrate the invention. However, it should be understood that theinvention is not intended to be limited to the specific embodiment.

3 EXAMPLE 20 parts by weight of an alcohol-moist nitrocellulose (basedon dry nitrogen content) having a nitrogen content of 13.15%, preparedfrom SW containing 13.35% nitrogen and CWS containing 12.6% nitrogen,and 100 parts by weight of nitroglycerin were mixed with agitation andallowed to stand for several hours to form a sectile gelatin. Thegelatin mass is then powdered to obtain a preconcentrate. The powderedpreconcentrate was processed with additional alcohol-moistnitrocellulose, nitroguanidine and Akardit II (methyl diphenylurea) inthe amounts set forth in the following Table I to obtain a 15 kg. batchof material plus 1.7 kg. of acetone.

TABLE I The ingredients of Table I were thoroughly kneaded in a kneadingmachine for about 2 /2 hours and the mixture was then cured at roomtemperature for 8 to 14 days. The mass was then extruded with anextrusion press and cut into 2 mm. lengths screened and dried undervacuum. The so-called White grain (because of white color due tonitroguanidine content) was subjected for half an hour to treatment withwater at 50 C. with mechanical agitation and was dried. The resulting 15kg. of white grain composition was then subjected to a four stagesurface treatment in drums to apply the desensitizers.

In the first stage, the grains were sprayed with 4 equal portions of a0.6% solution of 0.024 kg. of dibutyl phthalate in 0.292 kg. of 94%alcohol at 40 to 42 C. The second and third stages were the same usingas the treatment solution, 0.8% solution of 0.0332 kg. of dibutylphthalate in 0.227 kg. of 94% alcohol (2nd stage) and 1.0% solution of0.040 kg. of dibutyl phthalate in 0.162 kg. of 94% alcohol (3rd stage).In the fourth stage, the solution used was 0.6% solution of 0.024 kg. ofN,N- diethyl-carbanilide in 0.162 kg. of 94% alcohol. After cooling, theresulting powder is removed from the treatment drums and dried in anoven at 50 C. for five hours to attain the desired moisture content.Depending upon the number of treatment stages, the total treatment timewill be beween 4 and 32 hours. The resulting powder has a high caloriccontent but has a progressive combustion rate with a considerableincrease of the resulting gas volume making it suitable for highballistic Weapons.

The energy content of the preconcentrate of the example could beincreased by the addition of other explosives such as trinitrotoluol andother water-soluble, nitrogen containing compounds such as ammoniumperchlorate could be used.

Various modifications of the process and products of the application maybe made without departing from the spirit or scope thereof and it is tobe understood that the invention is to be limited only as defined in theappended claims.

We claim:

1. A process for the preparation of a double-base or triple-basenitrocellulose powder propellant having a progressive rate of combustioncomprising forming a polybasic powder propellant containing awater-soluble, nitrogen-rich compound, surface treating the resultingpropellant with an aqueous media to dissolve the said watersolublecompound from the outer layers of the propellant and introducing intothe resulting pores in the propellant and on the surface of thepropellant a desensitizer to obtain a. polybasic propellant with aprogressive combustion rate.

2. The process of claim 1 wherein the treatment with the aqueous mediais etfected at 50 to C.

3. The process of claim 1 wherein the introduction of the desensitizeris a. multistep treatment.

4. The process of claim 1 wherein the polybasic propellant is a mixtureof nitrocellulose and nitric acid esters of polyvalent alcohols.

5. The process of claim 1 wherein the water-soluble, nitrogen-richcompound is selected from the group consisting of nitroguanidine,guanidine nitrate, ammonium nitrate and dicyanodiamide.

6. The process of claim 1 wherein after the first step, thesolvent-moist powder is subjected to an intermediate wet storage.

7. The process of claim 1 wherein after the first and/or following stepof introducing the desensitizer, the powder is subjected to dry storage.

8. The process of claim 1 wherein after introduction of thedesensitizer, the solvent-moist powder is subjected to an intermittentwet storage.

9. The process of claim 1 wherein after introduction of thedesensitizer, the powder is subjected to dry storage.

References Cited CARL 'D. QUARFORTH, Primary Examiner P. A. NELSON,Assistant Examiner U.S. Cl. X.R. 149-1 1, 98,

